The invention relates to a suspended ceiling grid network which utilizes clips to connect a primary grid member to a secondary or cross grid member in a generally perpendicular relationship. More specifically, the invention relates to a grid network having a clip which permits lateral movement of the cross grid member relative to the primary grid member in at least two horizontal directions with respect to the ceiling plane, while maintaining the assembled relationship of the primary and cross grid members.
Clips for securing two grid members in generally perpendicular relation to one another in order to form a ceiling grid network are widely known in the art. In geographical regions subject to earthquakes, steel buildings are designed with lateral force resisting (seismic) systems to resist the effects of earthquake forces. Seismic systems make a building stiffer against horizontal forces, thus minimizing the amount of relative lateral movement and resultant damage. Although the buildings may be designed structurally to provide seismic resistance to lateral forces, suspension ceiling systems remain very susceptible to displacement under seismic conditions.
ASTM E 580-02 provides a standard practice for “Application of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Requiring Seismic Restraint.” This standard practice covers acoustical ceiling suspension systems and their additional requirement for application both in areas subject to light to moderate seismic disturbance such as Uniform Building Code (UBC) Seismic Zone 2, and areas subject to moderate to severe seismic disturbance such as UBC Seismic Zones 3 and 4. The intent of this standard practice is to provide an unrestrained ceiling system designed to accommodate the horizontal movement of the grid network when loads are applied laterally to a ceiling surface, such as during a seismic event. ASTM E 580-02 requires, in areas subject to light to moderate seismic disturbance, that the primary and cross grid members of the ceiling system, including their splices, connectors and expansion devices be designed and built to carry an average test load of 60 lbs. in tension with a 5 degree misalignment of the primary and cross grid members in any direction.
Typically, a ceiling system having a ceiling area of less than 2500 square feet, is attached to the wall via wall angles on two adjacent sides. On the other two sides, wall angles with 2 inch horizontal legs are used along with spacer bars and hanger wires. Thus, during a seismic event, the grid members abutting the wall can move laterally away from the wall, i.e. float on the 2 inch perimeter wall angle. The 2 inch wall angles provide the 5 degree misalignment of the primary and cross runners in the direction of the horizontal ceiling plane as required by ASTM E 580-02.
In order to comply with ASTM E 580-02 at an interior ceiling location, one solution that has been contemplated by those skilled in the art is to utilize primary and cross grid members having four inch horizontal flanges, in other words, two inch flanges on either side of the vertical web. This solution effectively provides the same effect as the 2 inch wall angles at an interior ceiling location. However, from an aesthetic standpoint, it is undesirable to use grid members having such wide flanges.
Additionally, the 2000 International Building Code specifies that “for ceiling areas exceeding 2500 square feet a seismic separation joint or full height partition shall be provided.” Essentially, this requires a large ceiling area to be segmented into independent smaller areas to prevent the ceiling from completely collapsing during a seismic event.
In order to comply with both ASTM E 580-02 and the 2000 International Building Code, a grid network is needed which eliminates primary grid members having 4 inch lower flanges and which partitions a single ceiling area into smaller independent ceiling areas.